In Patent Literature 1, there is a description of supplying a high-frequency low voltage to a compressor during a shutdown at the time of heating. In Patent Literature 2, there is a description of supplying a single-phase AC voltage having a higher frequency, e.g., 25 kHz, than that at the time of normal operation to a compressor when the temperature of the air conditioner's surroundings becomes low.
The techniques described in Patent Literatures 1 and 2 are both for facilitating a lubricating action in the compressor by heating the compressor or keeping the compressor warm by applying a high-frequency AC voltage to the compressor in accordance with a decrease in outside air temperature.